It has already been well recognized that there is a need for a plant watering device which will ensure an adequate supply of water to a plant after a considerable lapse of time and without human intervention, after initial setting up of the device.
Thus, for example, a person leaving his or her dwelling for a period of time, for example for the purpose of a vacation, often requires to ensure that a plant in the dwelling is adequately irrigated during that period of time but, nevertheless, frequently desires to avoid overwatering of the plant and, also, to avoid granting access to another person to the dwelling for the purpose of watering the plant.
Various attempts have been made in the past to provide a watering device which fulfills such a purpose by providing a constant, possibly very slow, supply of water to a plant, or by effecting a delayed supply of water to the plant.
For example, one prior watering device comprises a tray to be placed under a pot containing the plant, with a wick extending from the tray through the base of the pot and terminating in a potting mix within the pot, so that water is drawn up the wick by a wicking action.
Another prior device comprises a large tray fitted with a porous styrofoam base for a plant pot and, in that case, moisture percolated up to the pot from the tray by capillary action trough the styrofoam base.
Another prior suggestion is a cone shaped device made of pottery, which is glazed at the open end of the cone-shaped device, the opposite, pointed end of the device being closed but remaining unglazed, so that when the cone is inverted and pushed into the soil, and the inside of the device is filled with water, the water is slowly released through the pointed end of the device to water the plant and, thereby, to prevent it from drying out.
It will be appreciated that the above-described devices are intended to effect constant watering of a plant, rather than providing a delayed supply of water to the plant after a period of time during which no watering occurs.
A further prior art watering device is shown in U.S. Pat. No. 267,296, which teaches a self-irrigating flower pot or vase in which apertures allow water to pass from a reservoir into a saucer and then into the pot. Evaporation from the saucer and absorption of water in the pot cause the liquid level in the saucer to fall below the apertures, which allows further water to flow from the reservoir. Once again, this prior device constantly waters the pot.
U.S. Pat. No. 3,125,255, issued Mar. 17, 1964 to B. Kaiser, shows the use of evaporation from an auxiliary reservoir to control air flow into a main reservoir and, thus, to control the outflow of water from the main reservoir. More particularly, according to the teachings of this prior device, evaporation from a so-called water receiver uncovers the lower end of a tube, to allow air to flow into a main container, which in turn allows water to flow therefrom through an outlet.
While the device shown in the aforesaid U.S. Pat. No. 3,125,255 effects delayed watering of a plant or the like, by employing evaporation in a separate water chamber to delay the onset of irrigation, as described above, it nevertheless simply allows a single flow of water from the main container at a delayed period of time but in a continuous manner, and does not in any way enable an intermittent, i.e. repeated, watering action to be effected.
Further prior art watering devices are shown in U.S. Pat. Nos. 3,438,575; 4,060,934; 4,085,546; 4,121,608; 4,241,538 and 4,542,762.